Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27M—WORKING OF WOOD NOT PROVIDED FOR IN SUBCLASSES B27B - B27L; MANUFACTURE OF SPECIFIC WOODEN ARTICLES
  • B27M3/00—Manufacture or reconditioning of specific semi-finished or finished articles
  • B27M3/0013—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles
  • B27M3/002—Manufacture or reconditioning of specific semi-finished or finished articles of composite or compound articles characterised by oblong elements connected at their ends
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
  • C09J161/04—Condensation polymers of aldehydes or ketones with phenols only
  • C09J161/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
  • C09J161/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
  • C09J161/22—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
  • C09J161/24—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with urea or thiourea
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
  • C09J5/02—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers involving pretreatment of the surfaces to be joined
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/19—Sheets or webs edge spliced or joined
  • Y10T428/192—Sheets or webs coplanar
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31942—Of aldehyde or ketone condensation product
  • Y10T428/31949—Next to cellulosic
  • Y10T428/31957—Wood

Definitions

• the present invention comprises a method of joining pieces of wood.
• finger-joint One type of glued connection which is widely used in the timber processing industry is the finger-joint. This joint is made by a process whereby wedge-shaped fingers are machined into the end of side-grain of the pieces of timber to be joined, adhesives developed for joining timbers are applied to the exposed faces of the fingers, the fingers on any two pieces of wood are mated so that the protruding fingers on one piece of timber will slide into the grooves cut on the other piece, and end pressure is applied so that the wedge-shaped fingers "lock” together. The end pressure will also supply sufficient lateral pressure to the adhesive between the sloping faces of the fingers that the adhesive will satisfactorily bond the two pieces of timber together with sufficient strength and reliability that the resulting piece will be usable in load bearing situations. Finger-jointing is widely used to produce longer, finger-jointed lengths of good quality timber from wood having an unacceptably high number of defects.
• This conventional finger-jointing process described above requires seasoned timber i.e. dried to moisture content below fibre saturation point before joining and preferably at around 12% moisture content, to achieve the required strength and reliability.
• the timber may be seasoned by air drying, or by a drying process such as kiln drying. Air drying is suitable in some situations but the time involved being many weeks precludes its use in favor of a drying process such as kiln drying in many cases.
• unseasoned timber i.e. fleshly cut wood from logs or partially dried after cutting
• the lengths of timber after sawing from the log are kiln-dried or air-dried, and then sections containing defects such as knots etc. are cut from the lengths of timber leaving short lengths of high grade, dry timber. These short lengths of high grade timber are then finger-jointed to produce continuous lengths of timber which are finally cut to required length for commercial sale.
• Seasoned timber is required for finger-jointing and other applications because the adhesives most often used are soluble in water. Free water present in the cell lumens of unseasoned timber can flow into the newly made joint, mix with the as yet uncured adhesive, and the adhesive can then dissolve into the water and migrate away from the joint. By the time the adhesive has cured naturally, the joint is lacking in adhesive and has insufficient adhesive present and a very weak joint results.
• a method of joining pieces of unseasoned wood comprises the steps of joining the pieces of wood with an adhesive formulation of a sufficiently high molecular weight or viscosity to avoid adhesive degradation or migration in situ in the joint by moisture from the wood during forming and curing of the joint, or which will cure to achieve a sufficiently high molecular weight or viscosity in a time sufficient to avoid adhesive degradation or migration in situ by moisture from the wood during forming and curing of the joint.
• the adhesive is cured without application of heat.
• the invention may be said to comprise a method for joining pieces of unseasoned wood comprising joining the pieces of wood with an adhesive formulation of a sufficiently high molecular weight or viscosity to avoid adhesive degradation or migration in situ in the joint by moisture from the wood during forming and curing of the joint, or to achieve a sufficiently high molecular weight or viscosity which will cure in a time sufficient to avoid adhesive degradation or migration in situ moisture from the wood during forming and curing of the joint.
• the method includes removing defect material from longer lengths of wood containing defects to produce shorter lengths of higher grade, unseasoned timber and then finger-jointing the shorter lengths of unseasoned timber with the adhesive and curing the adhesive, preferably without the application of heat.
• a high molecular weight or viscosity adhesive may be produced by aging an adhesive formulation of conventional viscosity and/or molecular weight so that preferably less than 50% of the normal pot life of the adhesive remains.
• Adhesives suitable after aging that may be employed are any adhesive formulations that will age to the required viscosity and molecular weight including formaldehyde based adhesives such as resorcinol formaldehyde, phenol formaldehyde, and urea formaldehyde.
• Additional hardener or accelerant or other additives, such as ammonium chloride and boric acid for example may be added to the adhesive formulation to accelerate aging.
• a retardant is added to reduce the rate of aging, that is to increase the subsequent pot life of the adhesive, once the adhesive formulation has aged to the required viscosity and/or molecular weight for use in the method of the invention.
• the adhesive may have a viscosity in the range of 7000 to 10,000 centipoise. However, adhesives having a viscosity outside this range may be employed.
• the adhesive may have a lower viscosity but the adhesive should have a sufficiently high viscosity to reduce the solubility and prevent migration away from the joint due to the presence of moisture.
• the viscosity of the adhesive may be higher provided that the viscosity of the adhesive is not so high that the adhesive may not be properly coated on the wood fingers.
• an adhesive formulation having a base polymer which is highly branched or high molecular weight linear polymer is employed.
• These types of polymer are generally desolubilized on dilution with water. Suitable examples that may be mentioned are melamine urea formaldehyde in particular and resorcinol formaldehyde that have added a branching agent such as urea or melamine.
• the adhesive employed is a formaldehyde based adhesive.
• the formaldehyde based adhesive comprises at least one hydroxy or amino functionalized aromatic component. Examples of such components include phenol, aniline, resorcinol, catechol, phloroglucinol, tannin, and flavonoid compounds, and the like.
• the formaldehyde based adhesive comprises amino formaldehyde condensate.
• examples of such adhesives include urea formaldehyde, melamine formaldehyde and casein formaldehyde.
• adhesives are formulations comprising resorcinol formaldehyde, phenol formaldehyde, phenol resorcinol formaldehyde, urea formaldehyde, phenol urea formaldehyde, tannin formaldehyde, melamine formaldehyde or melamine urea formaldehyde.
• Phenolic adhesives are preferred and most preferred are resorcinol formaldehyde and phenol resorcinol formaldehyde.
• the adhesive may be applied by any conventional technique for adhesive application in finger-jointing or other wood joining techniques, at usual application rates.
• the adhesive formulation is a high viscosity molecular weight formulation or not
• the adhesive is contacted with a cure promotor chemical which increases the rate of cure of the adhesive on forming of the joint.
• the cure promotor chemical is applied to wet one or both of the bonding surfaces of the wood, such as the fingers in a finger-joint, prior to application of the adhesive.
• an adhesive system can comprise a reactive component kept prior to use at a pH suitable for minimum curing, and a second adhesive component compatible with the first part and which when contacted therewith in use renders the combination highly reactive towards adhesive curing.
• the adhesive curing rate is dependent on pH. Because of adhesive pot-life considerations, the pH range is normally held from approximately pH 1 to 8, in particular for fast curing adhesive formulations.
• the formulation of a two-part adhesive is an undesirable complication, and we have found that application of a simple pre-treatment chemical to one (or optionally both) of the bonding surfaces will achieve the same result as when using a formulated two-part adhesive system.
• the cure promotor chemical could be contacted with the adhesive by being injected or added into the adhesive supply line immediately before application of the adhesive to the wood, in a finger-jointing or plywood manufacture plant for example.
• One class of preferred cure promotor chemical is basic chemicals (pH>7) which will react on contact with the adhesive to change the nature of a conventional adhesive to a fast curing adhesive.
• One class of preferred cure promotor chemicals comprises ammonia or an amine or amine derivative compound.
• ammonia or amine or amine derivative compound is applied in solution at least 10% by weight, but ammonia could be applied as a gas to the wood surfaces as it will solubilize on contact with wood moisture.
• Another class of preferred cure promotor chemicals is organic acids such as low molecular weight carboxylic acids i.e. carboxylic acids having a molecular weight below 300 and most preferably below 150, applied in solution of at least 50% by weight and preferably at least 80% or above by weigh, including formic acid and trichloroacetic acid.
• carboxylic acids having a molecular weight below 300 and most preferably below 150
• formic acid and trichloroacetic acid including formic acid and trichloroacetic acid.
• cure promotor chemicals is Lewis and Bronsted acids, preferably comprising a transition metal ion component such as chromium applied as chromic acid, zincs salts, aluminum salts, and the like.
• a further class of cure promotor chemical is volatile organic acids applied at high concentrations such as 90% formic acid, trifluoroacetic acid, and the like.
• the bonding surfaces of the wood may be surface dried.
• surface dried in the context of this invention is meant that the mating surfaces of the wood are heated without heating the body of the pieces of wood.
• surface heating for a time in the range of 30 to 120 seconds is preferred, by blowing hot air over the wood surfaces, for example.
• the joined pieces of wood may then be dried, for example, by artificial drying or simply by air seasoning.
• the unseasoned finger-jointed lengths of timber may then be kiln dried.
• Wood with a moisture content that would conventionally be regarded as too high for successful jointing by gluing or adhesion can be bonded before drying by the method of the invention.
• unseasoned wood wood having a moisture content in excess of 30%.
• the method can be used with wood having a moisture content in excess of 50 or even 100%.
• the method of the invention enables defects to be removed from the green timber before further processing so that defect wood is not further processed. In the case of drying for example, energy is not wasted in drying defect material.
• the method of the invention also makes available to unseasoned timber products such as framing the benefits of upgrading by finger-jointing. For wood which does not require defect removal such as veneers which are cut from logs to form plywood, the process enables the veneers to be bonded together immediately after cutting while still in the green state, so that it is not necessary to season and then bond the veneers so that handling is reduced.
• Ten finger-jointed samples were made up by cutting the separate pieces of the unseasoned stock having a mean moisture content of 90% by weight to 335 mm lengths, machining finger profiles on one end of each length using Leitz 10/10 mini joint cutters in a Louis Eichmann finger-jointing machine with automatic damping of samples and passage of the sample past the rotating cutting heads.
• a batch of resorcinol formaldehyde resin was mixed up using standard formulation (4 resin:1 hardener by weight). Viscosity was measured using a Brookfield viscometer and found to be between 3000 and 4000 centipoise at 20° C. A period of time was allowed to pass until further tests showed viscosity had reached 7000 centipoise.
• This adhesive was then applied to one set fingers and the set of fingers with adhesive thereon were mated to another set of fingers with no adhesive. Clamping forces parallel to the grain direction were applied to the plain ends of the now joined lengths of timber, at a stress of 5.5 MPa, by pressing between the platens of a universal testing machine.
• the samples were dried at ambient temperature for a period of approximately 6 days and then conventionally kiln dried at 70° C. until the samples were at approximately 12% moisture content.
• Example 1 Sixteen finger-jointed samples were made up as in Example 1 from stock at 92% by weight means moisture content.
• the samples were dried in the laboratory at ambient temperature for a period of approximately 6 days then dried in a conventional kiln at 70° C. for 6 days until the samples were at approximately 12% moisture content.
• Example 2 Sixteen finger-jointed samples were made up as in Example 2 from stock at 149% by weight mean moisture content.
• Example 1 Twenty finger-jointed samples were made up as in Example 1 from stock having a mean moisture content of 78%. A solution of 5% chromic (V1) acid was sprayed onto the freshly cut surfaces of the fingers on each piece, then the fingers were flash dried, using a hot air gun for 30 seconds per piece, so that the tips of the fingers reached about 100° C., the base of the fingers reached about 50° C., but solid wood 1 cm in from the base of the fingers did not change in temperature appreciably from the ambient temperature of 20° C. There was no significant drop in moisture content of the fingers. Freshly mixed R15 resorcinol formaldehyde adhesive was applied to one set of fingers and the set of fingers with adhesive thereon were mated to another set of fingers with no adhesive. Clamping forces parallel to the grain direction were applied to the plain ends of the now joined lengths of timber, at a stress of 5.5 MPa, by pressing between the platens of a universal testing machine.
• V1 5% chromic
• the samples were dried in a force air dryer at ambient temperature for a period of approximately 4 weeks until the samples were at approximately 12% moisture content.
• One pair of slips was made from unseasoned (moisture saturated) radiata pine, otherwise complying with the requirements of British Standard 1204:Part 2.
• the bonding surface of one pine slip was dipped in a solution of triethanolamine (5 molar).
• Freshly mixed phenol resorcinol formaldehyde adhesive was applied to the bonding surface of the other pine slip and the two pine slips were mated.
• the samples were clamped, subsequently dried and tested as in Example 6. The results showed a failure shear force of 1.8 kN.
• Example 2 Ten finger-jointed samples were made up as in Example 1 using stock at a mean moisture content of 107%. A solution of 0.5 mole/liter sodium periodate was sprayed onto the freshly cut surface of the fingers of each piece. Freshly mixed R15 resorcinol formaldehyde adhesive was applied to one set of fingers and the set of fingers with adhesive thereon were mated to another set of fingers with no adhesive. Clamping forces parallel to the grain direction were applied to the plain ends of the now joined lengths of the timber, at a stress of 5.5 MPa, by pressing between the platens of a universal testing machine.
• the samples were dried in a forced air drier at ambient temperature for a period of approximately 4 weeks until the samples were at approximately 12% moisture content.
• Example 2 Ten finger-jointed samples were made up as in Example 1 using unseasoned (moisture saturated) radiata pine. A solution of 90% foric acid was sprayed onto the freshly cut surface of the fingers of each piece. Freshly mixed urea formaldehyde adhesive was applied to one set of fingers and the set of fingers with adhesive thereon were mated on another set of fingers with not adhesive. Clamping forces parallel to the grain direction were applied to the plain ends of the now joined lengths of timber, at a stress of 5.5 MPa, by pressing between the platens of a universal testing machine.
• the samples were dried in a forced air drier at ambient temperature for a period of approximately 4 weeks until the samples were at approximately 12% moisture content.
• unseasoned 100 ⁇ 50 mm radiata pine timber twenty finger-jointed 650 mm lengths were manufactured by cutting the separate pieces of the unseasoned stock to 335 mm lengths, and machining finger profiles on one end of each length using Leitz 10/10 mini joint cutters in a Louis Eichmann finger-jointing machine with automatic clamping of samples and passage of the sample past the rotating cutting heads.
• Freshly mixed resorcinol formaldehyde adhesive was applied to one set of fingers and the set of fingers with adhesive thereon were mated to another set of fingers with no adhesive and clamping forces parallel to the grain direction were applied to the plain ends of the now joined lengths of timber, at a stress of 5.5 MPa, by pressing between the platens of a universal testing machine.
• the samples were dried in a forced air drier at ambient temperature for a period of approximately 4 weeks until the samples were at approximately 12% moisture content.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Wood Science & Technology (AREA)
• Forests & Forestry (AREA)
• Chemical And Physical Treatments For Wood And The Like (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Veneer Processing And Manufacture Of Plywood (AREA)
• Standing Axle, Rod, Or Tube Structures Coupled By Welding, Adhesion, Or Deposition (AREA)

Priority Applications (1)

Applications Claiming Priority (5)

Related Parent Applications (1)

Publications (1)

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Cited By (22)

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Citations (9)

• 1990
  • 1990-12-21 NZ NZ260406A patent/NZ260406A/en unknown
• 1991
  • 1991-12-20 AT AT91311852T patent/ATE135032T1/de not_active IP Right Cessation
  • 1991-12-20 EP EP19910311852 patent/EP0493010B1/de not_active Expired - Lifetime
  • 1991-12-20 DE DE69117708T patent/DE69117708T2/de not_active Expired - Fee Related
  • 1991-12-20 AU AU89970/91A patent/AU652792B2/en not_active Ceased
  • 1991-12-20 SG SG1996006503A patent/SG52592A1/en unknown
  • 1991-12-20 ES ES91311852T patent/ES2084124T3/es not_active Expired - Lifetime
  • 1991-12-20 DK DK91311852T patent/DK0493010T3/da active
  • 1991-12-29 CA CA 2058165 patent/CA2058165C/en not_active Expired - Fee Related
• 1992
  • 1992-01-09 JP JP221392A patent/JP2749001B2/ja not_active Expired - Lifetime
• 1994
  • 1994-06-06 US US08/254,431 patent/US5674338A/en not_active Expired - Fee Related

Patent Citations (9)

Non-Patent Citations (3)

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